To get the source code of any SQL object in Oracle we can use a standard API(Package-function) DBMS_METADATA.GET_DDL
Syntax:
dbms_metadata.get_ddl('object_type','object_name')
Example:
select dbms_metadata.get_ddl('INDEX','SAM_IDX') from dual;
select dbms_metadata.get_ddl('INDEX','SAM_IDX') from dual;